A known variable valve timing control device is disclosed in Japanese Patent Laid-Open Publication No. H11(1999)-81928. The known variable valve timing control device is provided on a drive force transmission system for transmitting a drive force from a driving shaft of the internal combustion engine to a driven shaft for opening and closing at least one of an intake valve or an exhaust valve of an internal combustion engine. The known variable valve timing control device includes a housing, a vane rotor having vanes rotating relative to the housing within a predetermined angle range, and sealing members supported by the vane rotor to contact the housing for sealing the housing and the vane rotor. With the known variable valve timing control device disclosed in Japanese Patent Laid-Open Publication No. H11(1999)-81928, aluminum or an iron system metal is applied as the housing and the sealing member made of resin with lower hardness than the housing is applied to each tip end of the vane. Because the sealing members always slidingly contact to an internal surface of the housing, the sealing members with low hardness likely to be worn. In case the housing and the vane are applied with the same material such as aluminum, the abrasion may be increased. In this case, for example as shown in FIG. 2, when hard foreign materials (e.g., molding sand) included in engine oil are jammed between the vane and the housing during the sliding operation of the vane, the foreign materials are buried in sliding surfaces on the housing side and on the vane side. Thus, the buried foreign materials on the hosing side and on the vane side scrape the opposing sliding surfaces on the housing side and the vane side one another to accelerate the abrasion as aggressive abrasion. Thus, the performance of the variable valve timing control device may be deteriorated. And foreign materials generated by the sliding abrasion influence causing defects such as burning of a camshaft and an operation lock of an OCV (i.e., oil pressure control valve).
On the other hand, another known variable valve timing control device is disclosed in Japanese Patent Laid-Open Publication No. H01(1989)-092504. The known variable valve timing control device disclosed in Japanese Patent Laid-Open Publication No. H01(1989)-092504 includes a rotor for opening and closing a valve, a housing engaged with the rotor to be relatively rotatable, a vane provided to be slidably fitted in a vane groove formed on the rotor, a hydraulic chamber formed between the rotor and the housing and divided into an advance angle chamber and a retarded angle chamber by the vane, a first hydraulic passage for supplying or discharging the fluid to or from the advance angle chamber, and a second hydraulic passage for supplying or discharging the fluid to or from the retarded angle chamber. The vane fitted in the vane groove of the rotor is biased towards the housing side by a vane spring so that the rotor and the vane are unitary rotated. With the known variable valve timing control device, the vane groove on the rotor and the vane are repeatedly pushed against one another by the operation chamber hydraulic pressure. In addition, when the vane slides on an internal periphery of the housing in an peripheral direction, the vane slides in a radial direction due to a variation of a clearance between the rotor and the housing and the circularity error of the internal peripheral surface of the housing. When small and hard foreign materials (e.g., molding sand, sand invaded from outside) or carbon soot are invaded from the hydraulic pressure chamber of the variable valve timing control device, the sliding portion is abraded. Particularly, because the molding sand is harder than other foreign materials and has larger particle diameter compared to other foreign materials, the aggressive abrasion at the sliding portions may be caused. Further, in case the vane and the sliding surface of the sliding portion of the vane are ruined, the aggressive abrasion may advance quickly. Due to the influence of the foreign materials generated by the performance deterioration and the sliding abrasion of the variable valve timing control device, drawbacks such as burning of a camshaft and the operation lock of the oil pressure control valve (OCV) may be caused.
A need thus exists for a variable valve timing control device which includes high abrasion resistance between a housing and a vane and between a rotor and the vane for preventing a performance deterioration and defects.